That notion should be nothing new to Don Draper (Jon Hamm), a self-made man who fought to transform himself from Midwestern farm boy Dick Whitman into Madison Avenue's biggest fish. But following his sudden, impulsive proposal to his secretary Megan (Jessica Pare) in the Season 4 finale, Don may be done clawing his way to the top."One of the big questions that the show asks about the human condition is: Do people ever really change?" Hamm says. "I think [Don's] turned the page — he's starting a new chapter. I think he's trying to be a better man, trying to kind of pick up the pieces. But what happens when you're satisfied? Maybe you lose some of that fire."Meanwhile, the fire in Pete Campbell (Vincent Kartheiser), who has long been the show's poster child for naked ambition, has never burned brighter. And with Roger (John Slattery) having lost Sterling Cooper Draper Pryce's most valuable client in Lucky Strike, Kartheiser says now is definitely the time to make others take notice.

"He's beginning to take on that role of boss man and realize his power in the situation," Kartheiser says of his character, who last season also welcomed a baby girl with his wife Trudy (Alison Brie). "[With] Pete having a young baby and not having a bank account stocked with money, he does have the fire in his belly. He's always been a very ambitious character... [but] now the pressure is on. It's only going to heighten his ambition."Pete's a very competitive sort," Kartheiser continues. "Sometimes he loses, and sometimes he wins. But I think he's learned by Season 5 which battles to fight and which ones he's going to win. [He knows] who he needs to support and fall behind and who he needs to try to lead and take down."Undoubtedly, his first target is Roger, who, now more than ever, is a figurehead in the corner office. "[Roger] is on unsteady ground," Slattery says. "His name is on the building, but does he even care? He isn't getting any younger in an environment that is becoming more youth-oriented. I think it is a difficult place for him to be."

But don't expect to see Roger go down without a fight. In fact, Slattery says he was shocked when many fans began to speculate that Roger was going to commit suicide in Season 4. "I don't see him as somebody who's going to check out on his own," Slattery says. "I think Roger is a pragmatist. [In Season 5] he's sort of taken a minute and judged his surroundings and he acts accordingly. He's not ready to go. I think he's not ready to sail off into the sunset."Of course Roger's struggles go beyond the business. In Season 4, he fell back into an affair with Joan (Christina Hendricks), who became pregnant with his child. Although Joan told Roger she went through with the abortion he arranged, she didn't, opting instead to tell her husband Greg (Sam Page), an Army doctor in Vietnam, that he had a little one the way.So what does that mean for Roger? "He's in flux," Slattery says. "The whole thing is up in the air. Obviously there is a connection with Joan, but that doesn't necessarily mean that [he's] going to throw everything over and live with [her]. I don't know whether he's prepared to do anything. Keeping up appearances is important to Roger."

Remarkably, on the sliding scale between Pete and Roger, Don is apparently much closer to Roger in Season 5. "What happens as you get older?" Hamm says. "What's the burning ambition that you once had? You can only maintain that for so long. And now we see it in Peggy [Elisabeth Moss]. We see it in Pete. These young kids are coming up and they're starting to have way more influence."Adds Kartheiser: "[Don] is very distracted. There's a big change going on. This is a time in America where there is a definite shift in the public's agenda. I don't know if Don has his finger on that the way he had his finger on the pulse of the 1950s."Mad Men premieres Sunday at 9/8c on AMC.Need a Season 4 refresher? Catch up on everything you need to know in two minutes below: